The present invention relates to graphics plotters and, more particularly, to a convertible platen for use in a drum plotter having vacuum columns and supply/takeup rollers wherein two platens are disposed with one on either side of the drum and with each being movable between a raised position spanning the vacuum column to create a table for cut paper movement and a lowered position allowing access to the vacuum column and forming a curved upper surface over which the roll paper smoothly flows to and from the roller.
In a drum type graphics plotter, a strip of paper (or other writing medium) is typically moved across the drum bi-directionally by being held against the surface of the drum at a rolling point of contact by a pinch roller while the drum is driven in response to a signal. Simultaneously, a writing head is moved traversely across the drum carrying a pen or other writing device in contact with the paper surface. The plot to be created in the X and Y directions is accomplished as a result of the bi-directional longitudinal movement of the paper in combination with the traverse movement back and forth of the head across the paper.
Typically, two types of paper are used--roll and cut. With roll paper, the paper extends from a supply/takeup roller across the drum to a second supply/takeup roller. To isolate the paper roll high inertia from the drum drive, so as to keep drum drive inertia low, and help facilitate quick start/stop moves, a vacuum column is disposed between each of the supply/takeup rollers and the drum in much the same manner as vacuum columns are employed in magnetic tape drives used with computer systems. For cut paper, on the other hand, a table is provided extending outwardly from the drum in either direction. The table supports the paper, which is of cut or fixed length, as it moves back and forth across the surface of the drum. The size of the table horizontally and the height of the surface of the drum from the floor determine the total length of the cut paper that can be employed. Typically, a drum graphics plotter is adapted to employ roll paper or cut paper, but not both.
Wherefore, it is the object of the present invention to provide apparatus for incorporation into a drum graphics plotter which will allow the combined ability to use either roll paper or cut paper effectively.